Exploring criticality in the QCD-like two quark flavour models

TL;DR

This paper investigates the critical phenomena in two-flavor QCD-like models, analyzing the critical end-point and tricritical point, and how various model components influence the critical behavior and phase diagram.

Contribution

It locates the tricritical point in effective QCD models and compares the critical behavior with and without fermionic vacuum contributions and Polyakov loop potential.

Findings

The tricritical point's proximity to the critical end-point is quantified.

Contours of susceptibilities reveal the shape of the critical region.

Critical exponents are calculated and compared across models.

Abstract

The critical end-point (CEP) and critical behaviour in its vicinity, has been explored in the two flavour effective chiral models with and without the presence of effective Polyakov loop potential.The tricritical point (TCP) in the massless chiral limit has been located on the phase diagram in the \mu andT plane for the Polyakov loop extended Quark Meson Model (PQM) and pure Quark Meson (QM) model which become effective Quantum-chromodynamics (QCD) like models due to the proper accounting of fermionic vacuum loop contribution in the effective potential.The proximity of the TCP to the QCD critical end-point (CEP) has been quantified in the phase diagram. The critical region around CEP has been obtained in the presence as well as the absence of fermionic vacuum loop contribution in the effective potentials of PQM and QM models. The contours of appropriately normalized constant quark number susceptibility and scalar susceptibility have been plotted around CEP in different model scenarios. These contours determine the shape of critical region and facilitate comparisons in different models such that the influence of fermionic vacuum term and Polyakov loop potential on the critical behavior around CEP can be ascertained in qualitative as well as quantitative terms. Critical exponents resulting from the divergence of quark number susceptibility at the CEP,have been calulated and compared with in different model scenarios. The possible influence of TCP on the critical behavior around CEP, has also been discussed. The temperature variation of \sigma and \pi meson masses at \mu = 0, \mu = \mu_ CEP and \mu > \mu_CEP has been shown and compared with in different model scenarios and the emerging mass degeneration trend in the \sigma and \pi meson mass variations has been inferred as the chiral symmetry restoration takes place at higher temperatures.